/* Copyright 1998 by the Massachusetts Institute of Technology.
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */
#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H
#  include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#  include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#  include <arpa/inet.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#  include <arpa/nameser.h>
#else
#  include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#  include <arpa/nameser_compat.h>
#endif

#include "ares.h"
#include "ares_inet_net_pton.h"
#include "ares_platform.h"
#include "ares_private.h"

#ifdef WATT32
#undef WIN32
#endif

struct addr_query {
	/* Arguments passed to ares_gethostbyaddr() */
	ares_channel channel;
	struct ares_addr addr;
	ares_host_callback callback;
	void *arg;

	const char *remaining_lookups;
	int timeouts;
};

static void next_lookup(struct addr_query *aquery);
static void addr_callback(void *arg, int status, int timeouts,
	unsigned char *abuf, int alen);
static void end_aquery(struct addr_query *aquery, int status,
	struct hostent *host);
static int file_lookup(struct ares_addr *addr, struct hostent **host);
static void ptr_rr_name(char *name, const struct ares_addr *addr);

void ares_gethostbyaddr(ares_channel channel, const void *addr, int addrlen,
	int family, ares_host_callback callback, void *arg)
{
	struct addr_query *aquery;

	if (family != AF_INET && family != AF_INET6)
	{
		callback(arg, ARES_ENOTIMP, 0, NULL);
		return;
	}

	if ((family == AF_INET && addrlen != sizeof(aquery->addr.addrV4)) ||
		(family == AF_INET6 && addrlen != sizeof(aquery->addr.addrV6)))
	{
		callback(arg, ARES_ENOTIMP, 0, NULL);
		return;
	}

	aquery = ares_malloc(sizeof(struct addr_query));
	if (!aquery)
	{
		callback(arg, ARES_ENOMEM, 0, NULL);
		return;
	}
	aquery->channel = channel;
	if (family == AF_INET)
		memcpy(&aquery->addr.addrV4, addr, sizeof(aquery->addr.addrV4));
	else
		memcpy(&aquery->addr.addrV6, addr, sizeof(aquery->addr.addrV6));
	aquery->addr.family = family;
	aquery->callback = callback;
	aquery->arg = arg;
	aquery->remaining_lookups = channel->lookups;
	aquery->timeouts = 0;

	next_lookup(aquery);
}

static void next_lookup(struct addr_query *aquery)
{
	const char *p;
	char name[128];
	int status;
	struct hostent *host;

	for (p = aquery->remaining_lookups; *p; p++)
	{
		switch (*p)
		{
		case 'b':
			ptr_rr_name(name, &aquery->addr);
			aquery->remaining_lookups = p + 1;
			ares_query(aquery->channel, name, C_IN, T_PTR, addr_callback,
				aquery);
			return;
		case 'f':
			status = file_lookup(&aquery->addr, &host);

			/* this status check below previously checked for !ARES_ENOTFOUND,
			   but we should not assume that this single error code is the one
			   that can occur, as that is in fact no longer the case */
			if (status == ARES_SUCCESS)
			{
				end_aquery(aquery, status, host);
				return;
			}
			break;
		}
	}
	end_aquery(aquery, ARES_ENOTFOUND, NULL);
}

static void addr_callback(void *arg, int status, int timeouts,
	unsigned char *abuf, int alen)
{
	struct addr_query *aquery = (struct addr_query *) arg;
	struct hostent *host;
	size_t addrlen;

	aquery->timeouts += timeouts;
	if (status == ARES_SUCCESS)
	{
		if (aquery->addr.family == AF_INET)
		{
			addrlen = sizeof(aquery->addr.addrV4);
			status = ares_parse_ptr_reply(abuf, alen, &aquery->addr.addrV4,
				(int)addrlen, AF_INET, &host);
		}
		else
		{
			addrlen = sizeof(aquery->addr.addrV6);
			status = ares_parse_ptr_reply(abuf, alen, &aquery->addr.addrV6,
				(int)addrlen, AF_INET6, &host);
		}
		end_aquery(aquery, status, host);
	}
	else if (status == ARES_EDESTRUCTION)
		end_aquery(aquery, status, NULL);
	else
		next_lookup(aquery);
}

static void end_aquery(struct addr_query *aquery, int status,
	struct hostent *host)
{
	aquery->callback(aquery->arg, status, aquery->timeouts, host);
	if (host)
		ares_free_hostent(host);
	ares_free(aquery);
}

static int file_lookup(struct ares_addr *addr, struct hostent **host)
{
	FILE *fp;
	int status;
	int error;

#ifdef WIN32
	TCHAR PATH_HOSTS[MAX_PATH];
	win_platform platform;

	PATH_HOSTS[0] = '\0';

	platform = ares__getplatform();

	if (platform == WIN_NT) {
		TCHAR tmp[MAX_PATH];
		HKEY hkeyHosts;

		if (RegOpenKeyEx(HKEY_LOCAL_MACHINE, WIN_NS_NT_KEY, 0, KEY_READ,
			&hkeyHosts) == ERROR_SUCCESS)
		{
			DWORD dwLength = MAX_PATH;
			RegQueryValueEx(hkeyHosts, DATABASEPATH, NULL, NULL, (LPBYTE)tmp,
				&dwLength);
			ExpandEnvironmentStrings(tmp, PATH_HOSTS, MAX_PATH);
			RegCloseKey(hkeyHosts);
		}
	}
	else if (platform == WIN_9X)
		GetWindowsDirectory(PATH_HOSTS, MAX_PATH);
	else
		return ARES_ENOTFOUND;

	wcscat_s(PATH_HOSTS, wcslen(WIN_PATH_HOSTS), WIN_PATH_HOSTS);

#elif defined(WATT32)
	extern const char *_w32_GetHostsFile(void);
	const char *PATH_HOSTS = _w32_GetHostsFile();

	if (!PATH_HOSTS)
		return ARES_ENOTFOUND;
#endif

	_wfopen_s(&fp, PATH_HOSTS, L"r");
	if (!fp)
	{
		error = ERRNO;
		switch (error)
		{
		case ENOENT:
		case ESRCH:
			return ARES_ENOTFOUND;
		default:
			DEBUGF(fprintf(stderr, "fopen() failed with error: %d %s\n",
				error, strerror(error)));
			DEBUGF(fprintf(stderr, "Error opening file: %ls\n",
				PATH_HOSTS));
			*host = NULL;
			return ARES_EFILE;
		}
	}
	while ((status = ares__get_hostent(fp, addr->family, host)) == ARES_SUCCESS)
	{
		if (addr->family != (*host)->h_addrtype)
		{
			ares_free_hostent(*host);
			continue;
		}
		if (addr->family == AF_INET)
		{
			if (memcmp((*host)->h_addr, &addr->addrV4,
				sizeof(addr->addrV4)) == 0)
				break;
		}
		else if (addr->family == AF_INET6)
		{
			if (memcmp((*host)->h_addr, &addr->addrV6,
				sizeof(addr->addrV6)) == 0)
				break;
		}
		ares_free_hostent(*host);
	}
	fclose(fp);
	if (status == ARES_EOF)
		status = ARES_ENOTFOUND;
	if (status != ARES_SUCCESS)
		*host = NULL;
	return status;
}

static void ptr_rr_name(char *name, const struct ares_addr *addr)
{
	if (addr->family == AF_INET)
	{
		unsigned long laddr = ntohl(addr->addrV4.s_addr);
		unsigned long a1 = (laddr >> 24UL) & 0xFFUL;
		unsigned long a2 = (laddr >> 16UL) & 0xFFUL;
		unsigned long a3 = (laddr >> 8UL) & 0xFFUL;
		unsigned long a4 = laddr & 0xFFUL;
		sprintf(name, "%lu.%lu.%lu.%lu.in-addr.arpa", a4, a3, a2, a1);
	}
	else
	{
		unsigned char *bytes = (unsigned char *)&addr->addrV6;
		/* There are too many arguments to do this in one line using
		 * minimally C89-compliant compilers */
		sprintf(name,
			"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.",
			bytes[15] & 0xf, bytes[15] >> 4, bytes[14] & 0xf, bytes[14] >> 4,
			bytes[13] & 0xf, bytes[13] >> 4, bytes[12] & 0xf, bytes[12] >> 4,
			bytes[11] & 0xf, bytes[11] >> 4, bytes[10] & 0xf, bytes[10] >> 4,
			bytes[9] & 0xf, bytes[9] >> 4, bytes[8] & 0xf, bytes[8] >> 4);
		sprintf(name + strlen(name),
			"%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.%x.ip6.arpa",
			bytes[7] & 0xf, bytes[7] >> 4, bytes[6] & 0xf, bytes[6] >> 4,
			bytes[5] & 0xf, bytes[5] >> 4, bytes[4] & 0xf, bytes[4] >> 4,
			bytes[3] & 0xf, bytes[3] >> 4, bytes[2] & 0xf, bytes[2] >> 4,
			bytes[1] & 0xf, bytes[1] >> 4, bytes[0] & 0xf, bytes[0] >> 4);
	}
}